1. Field of the Invention
Double-stranded molecular complexes.
2. Description of the Relevant Art
The formation of polymeric complexes where two different synthetic polymers are in side-by-side, intimate, contact is difficult. There are only a few examples where two polymers can be blended to form an intimate polymeric complex. A possible reason for this difficulty is the great entropy barrier that exists for two different polymers"" side-by-side intimate contact. This kind of entropy barrier is referred to as entropic frustration.
The object of a template-guided synthesis, see U.S. Pat. No. 5,489,400, is to reduce this entropy barrier by attaching monomers to the backbone of a polymer. The polymer acts as a template to arrange the monomers before they are polymerized. After polymerization very little rearrangement is necessary for the two polymer strands to form an intimate polymeric complex. The entropic frustration is released as the polymerization proceeds.
The template-guided synthesis is carried out in a series of steps. In step one, the monomers are attached to the backbone of a polymeric template to form an adduct. In step two, the adduct is acidified to form a precursor adduct. The addition of acid in this step controls the solubility of the template-guided synthesis product. In step three, the polymerization is initiated.
The present invention is a molecular complex comprising a conducting polymer and a biopolymer. The conducting polymer (CP) is selected from the group consisting of polyaniline, polypyrrole, polythiophene, poly(phenylenevinylene) or poly(phenylene sulfide) and substituted versions thereof. The biopolymer is selected from the group consisting essentially of proteins and nucleic acids including polynucleotides, e.g. DNA or RNA, polysacharrides, carbohydrates, etc. The invention comprises both the molecular complexes and the method of synthesizing the complexes. A particularly preferred embodiment comprises molecular complexes of polypyrrole and bovine serum albumin, polyaniline and bovine serum albumin, polypyrrole and human serum albumin and polyaniline and human serum albumin.
The molecular complexes can be usefully employed in anti-static coatings on films, e.g. photographs and as an antioxidant, e.g. to be carried by the bloodstream.
A biopolymer such as albumin is used as a template for the attachment of monomers. Once the monomers are added to albumin in solution, they attach or absorb onto the albumin to form a non-covalent intermolecular assembly, an adduct. The driving forces for adduct formation are thought to be electrostatic, hydrogen bonding and/or van der Waals forces.
The adduct is defined by the following symbol: (Py)x:BSA, (An)x:BSA, (Py)xHSA or (An)xHSA, where (Py)x=X pyrrole monomers, (An)x=X aniline monomers and represents a number of monomers bound non-covalently to the albumin, BSA=bovine serum albumin and HSA=human serum albumin.
In step two, the adduct is acidified to prepare the adduct for the subsequent polymerization reaction. A controlled amount of acid added in step two is helpful for the formation of stable water-dispersion of the reaction product in the subsequent step (step 3, the polymerization step). It is theorized that the additional acid causes an alteration of the degree of ionization of the anionic functional groups (e.g. the carboxylic acid groups) of the adduct and thus changes the conformation of the adduct. An adduct with intermediate degree of ionization results in stable dispersion without the formation of precipitation product. Although the polymerization of pyrrole can be achieved in a relatively wide range of pH (pH 0 to 7), the solution needs to be more acidic than pH 3 for the formation of green polyaniline product. In a solution with pH greater than 3, the polymerization reaction of aniline results in a brown product which is a mixture of polyaniline with a substantial amount of impurities.
In step three, the adsorbed pyrrole or aniline monomers in the adduct (for example, (Py)x:BSA, (An)x:BSA, (Py)x:HSA or (An)x:HAS) is polymerized to form the complex between the conducting polymer and the biopolymer. The polymerization reaction is induced by the addition of oxidants such as sodium persulfate, or ferric ions and hydrogen peroxide.